Lap plate

ABSTRACT

A lap plate for a lapping machine, the working surface of which is provided with a pattern of troughs through which an abrasive liquid centrifugally flows during a lapping operation, wherein the depth of the troughs can be varied in ratio to the wear of the surface of the lap plate.

United States Patent Day 51 Nov. 25, 1975 [54] LAP PLATE 3,128,5804/1964 Davis 51/209 R 3,324,607 6/1967 Niemiec... [75] Lawrence MountProspect m 3,745,645 7/1973 Kurth 241/294 [73] Assignee: Spitfire Tool &Machine Co., Inc.,

Chicago, 11L Primary Examiner-Al Lawrence Smith AssistantExaminer-Margaret M. Joyce 22 Fl (1. D 17, 1973 1 l 8 cc Attorney,Agent, or Firm-Edward C. Threedy [21] Appl. N0.: 425,328

[57] ABSTRACT [52] US. Cl. 51/209 DL [51] Int. Cl 824d 7/06 A lap platefor a lappmg machmei the workmg Surface S 5 1 6 29 DL Of which isprovided With a pattern Of troughs through 3 5 209 R which an abrasiveliquid centrifugally flows during a lapping operation, wherein the depthof the troughs [56] Reerences Cited can be varied in ratio to the wearof the surface of the UNITED STATES PATENTS 10/1962 Johnson 241/294 lapplate.

2 Claims, 5 Drawing Figures U,S. Patfint Nov. 25, 1975 3,921,342

LAP PLATE SUMMARY OF THE OPERATION In lapping operations, it isimportant to provide a suitable abrasive grit carried by a lubricatingmaterial, such as oil, evenly distributed upon the surface of therotating lap plate. The removal of stock from the workpieces and thefinishing of their lapped surfaces, as well as the resulting wear of thelap plate, are dependent not only on the extent of operation of the lapplate, but also on the uniformity of the abrading operation resultingfrom the continuous presence of an abrasive liquid over the entiresurface of the lap plate.

Thus, it is conventional practice to feed a liquid carrier, such aslight oil with abrasive material pollutions in suspension onto thesurface of the lap plate during its rotational lapping operation.

In order to be effective it is necessary that the abrasive material becontinuously maintained and evenly distributed upon the surface of thelap plate during its active period of abrading and then centrifugallyremoved beyond the periphery of the lap plate. To effect centrifugalremoval of spent abrasive material (material containing the stockremoved from the workpieces as well as from the surface of the lapitself), heretofore the surfaces of prior lap plates were provided witha pattern of troughs through which the abrasive material flowed.However, the depth of the troughs was such that they effected removal ofall of the abrasive liquid from the lap surface.

It is the purpose of the invention to provide a lap plate having itslapping surface provided with a pattern of troughs, the depth of whichcan be maintained so as to effectively remove only spent abrasive fluidswhile maintaining continuously a usable amount of abrasive fluidadjacent the surface of the rotating lap plate.

DESCRIPTION OF THE INVENTION The invention will be best understood byreference to the accompanying drawings showing one form of theinvention, and in which:

FIG. 1 is a fragmentary perspective view of a lapping machine containingthe invention;

FIG. 2 is a top plan view of the lap plate of the invention;

FIG. 3 is a fragmentary side elevational detailed sectional view of thelap plate of the invention;

FIG. 4 is fragmentary sectional view of one form of the invention; and

FIG. 5 is a fragmentary detailed sectional view of another form of theinvention.

The conventional lapping machine, such as shown in U.S. Pat. No.3,032,937 dated May 8, 1962, and one which may include the presentinvention, includes a base havng a circular top wall 11 within which isrotatably mounted a circular lap plate 12. Mounted upon the surface ofthe lap plate 12 are one or more work 'holders or wear rings 13, whichare adapted to be radially positioned upon the lap plate 12. A pressureplate 14 is positioned within the wear ring 13 and bears upon the worktherein which is to be lapped. So that the work may be placed in andremoved from the work holder 13, the pressure plate 14 is supported forvertical movement relative thereto by a unit 15 constructed and operatedin accordance with the aforesaid patent. The functional lapping machineis provided with a structure by which a liquid abrasive may be dispensedupon a surface of the lap plate 12. Such a liquid abrasive dispenser isindicated at 16 and may be of the construction and operation describedand shown in U.S. Pat. No. 3,261,510 dated July 19, 1966. This abrasivedispenser includes a delivery chute 17 through which the abrasivematerial is caused to flow onto a conically shaped dispensing cup 18removably positioned in a centrally formed well 19 in the lap plate 12.

By the use of the foregoing structure, an abrasive liquid may bedispensed onto the cup 18 and from thence over the lapping surface ofthe lap plate 12. This dispensing action is caused not only bycentrifugal force created by the rotational movement of the lap plate12, but also through the presence of the work holder 13 which is causedto rotate as a reaction to the rotation of the lap plate 12. The workholder 13 is caused to overlie a portion of the cup 18 so as tointerrupt the overflow of the abrasive liquid therefrom and by capillaryaction created by rotation of the work holder 13, the liquid is evenlyspread in a uniform film over the working surface of the lap plate 12.

The lap plate 12 may have its surface deformed by a pattern of troughs.This pattern may take the form of radially extending troughs such asthat shown in the aforementioned patents, or it may spirally extend fromthe well 19 to the outer edge of the lap or, as shown in FIGS. 1 and 2of the drawings, it may be formed in a cross-hatched pattern.

These troughs 20 are formed so as to intersect substantially at rightangles with respect to each other so as to extend completely across thelap plate 12 and so as to provide certain of the troughs, such as21-22-23 as well as 24-25-26, with open communication to the well 19formed in the center of the lap plate 12.

It is desirable to have the troughs 20 formed of a depth of 2.250 inchesand of a width of 0.125 inch, although the depth and width may varyaccording to the material from which the lap plate 12 is constructed.Each of the troughs 20 is filled with a non-abrasive, non-solublematerial 27 up to 0.0625 to 0.1875 inch of the top surface 28 of the lapplate 12, as shown in FIG. 4

As the lapping machine is operated, metal stock from the workpieces aswell as from the surface of the lap plate 12, is, through the presenceof the abrasive liquid, removed and suspended in the abrasive liquid. Itis desirable to remove the spent abrasive liquid upon the introductionof fresh abrasive fluid onto the surface 28 of the lap plate 12. This isaccomplished by causing the abrasive material to move not only over thelap surface 28 of the lap plate 12, but also through the troughs 20formed therein. Because of the cross-hatched pattern of arranging thetroughs 20, the centrifugal flow of the abrasive fluid toward theperipheral edge 29 of the lap plate 12, is through a tortious path byreason of the fact that the centrifugal force resulting from rotation ofthe lap plate 12 will extend through different lengths of troughs. Forexample, as shown in FIG. 2, when the lap plate 12 rotatescounterclockwise, the centrifugal force will follow the trough in thedirection of the arrow A and, as the lap plate 12 continues to rotate,that directional force will change and follow the direction of the arrowB, causing the abrasive liquid to follow such a changing path until itreaches the periphery 29 of the lap plate 12 where it is dispensed offthe lap surface 28.

By filling the troughs 20 with the non-abrasive, nonsoluble fillermaterial 27, the unspent abrasive liquid is maintained adjacent theworking surface 28 of the lap plate 12 and by its continuous presencecontinuously functions in the manner hereinbefore noted.

As the surface 28 of the lap plate 12 wears and approaches the uppersurface 30 of the filler material 27, such material through the use of asimple gauged tool may be routed out to the depth desired. Consequently,as the depth of the troughs may be maintained at the most efficientlevel in ratio to the work surface of the lap plate, the lapping machinedoes not have to be shut down for any material length of time forresurfacing of the lap surface or replacement of the lap plate.

In FIG. 5, I show a modified method of filling the troughs 20 formed inthe lap plate 12. In this modified form, the filler material 31 isplaced in the troughs in layers separated by a readily removable strip32. Thus, as it becomes necessary to regulate the depth of the troughs,one need only to strip off the separating strip 32, leaving intact alayer of filler material 31 at the prescribed depth desired.

While I have illustrated and described the preferred form ofconstruction for carrying my invention into effect, this is capable ofvariation and modification without departing from the spirit of theinvention. 1, therefore, do not wish to be limited to the precisedetails of construction set forth, but desire to avail myself of suchvariations and modifications as come within the scope of the appendedclaims.

Having thus described my invention, what I claim as new and desire toprotect by Letters Patent is:

1. A rotatable lap plate for a lapping machine over which an abrasiveliquid is caused to flow during a lapping operation, comprising a. asubstantially circular body carried in a horizontal plane by the machineand providing a working surface over which the abrasive liquid flows,

b. means formed in said body interrupting said working surface and intoand through which the abrasive liquid flows from said working surface,

. a removable filler in said means below said working surface of saidbody determining the depth of said means so as to regulate the amount ofabrasive liquid flowing therethrough and being gradually removable so asto maintain its relation to said working surface and the depth of saidmeans in relation to the wear of said working surface of said bodycaused by the lapping operation,

(1. and removable means embedded in said filler separating it intoindividual readily removable strips.

2. A rotatable lap plate as defined by claim 1, wherein said filler isformed from a non-abrasive nonsoluble material having a hardness lessthan the hardness of said body so as to be easily removed from saidmeans formed in said body.

1. A rotatable lap plate for a lapping machine over which an abrasiveliquid is caused to flow during a lapping operation, comprising a. asubstantially circular body carried in a horizontal plane by the machineand providing a working surface over which the abrasive liquid flows, b.means formed in said body interrupting said working surface and into andthrough which the abrasive liquid flows from said working surface, c. aremovable filler in said means below said working surface of said bodydetermining the depth of said means so as to regulate the amount ofabrasive liquid flowing therethrough and being gradually removable so asto maintain its relation to said working surface and the depth of saidmeans in relation to the wear of said working surface of said bodycaused by the lapping operation, d. and removable means embedded in saidfiller separating it into individual readily removable strips.
 2. Arotatable lap plate as defined by claim 1, wherein said filler is formedfrom a non-abrasive non-soluble material having a hardness less than thehardness of said body so as to be easily removed from said means formedin said body.